Ah. When you use the Enter key, WP assumes you want to enter a <p> tag, which gives the double line space between paragraphs. That's the normal way that HTML displays <p> tags (actually, the normal way that browsers display HTML <p> tags).

If you want to change it, edit your style.css -- but you may be surprised by what else changes.

OK, this is really getting me to reconsider my switch to WordPress. It does so many things but simply typing text like on a word prcoessor seems to be a huge undertaking.

And using a word processor is not like using a typewriter... Formatting web text is just not the same as formatting text with an offline word processor. If you want more or less space between paragraphs or line breaks, either edit theme's css or choose a better-spaced new theme. When writing posts with WordPress, two enters give you a new paragraph and one enter gives you a line break. I never bother with adding my own paragraph or line break tags.

The css you need to adjust is the margin or padding of p and/or line-height.

"Dean, mop your room floor?" demaned the cross dorm parent.
"Why should I have to do that? I pay to come to this school!"

I need no lines between paragraphs and tabs.

Just as with this forum's text, a single enter (return) after "cross dorm parent." should give you this result (a new line, not a new paragraph). Two enters (return return) after "to this school!"" will give you a new paragraph. New lines should not have extra added space around them.

Here's what your text here gets automatically transformed to look like in code form (WordPress does this automatically too):

<p>So how is this text done?</p>
<p>"Dean, mop your room floor?" demaned the cross dorm parent.<br />
"Why should I have to do that? I pay to come to this school!"</p>
<p> I need no lines between paragraphs and tabs.</p>

Just as with this forum's text, a single enter (return) after "cross dorm parent." should give you this result (a new line, not a new paragraph). Two enters (return return) after "to this school!"" will give you a new paragraph. New lines should not have extra added space around them.

I think that isn't exactly true. I can say also that my visual editor is acting a little silly since 2.6.2. Adding paragraphs and line breaks in strange places but only after the post is saved or published. It will not edit them real time if you switch views between visual or html, but it does insert a paragraph tag for me after only pressing enter once.

The proper way to do this would be using SHIFT + ENTER to only go down one line, at which point the visual editor should insert a BR.

I hope that makes sense and helps a little? I find that it does help to have a basic knowledge of HTML for situations like this, when the visual editor doesn't play 100% nice.